You can get a lot of study material from online. But i would like to suggest you buy official study material from Open Group Portal, only if you are more interested towards learn it on your own.
I would like to suggest you to go with free beginner videos available on the YouTube. Once you understand what it takes to become pro, you can opt in for premium training. Material for RPA Developer Advanced Course and several practice tests during the training will help you master the technology.
If you find it difficult towards self study and want someone to guide you, go with Mindmajix. Some of my friends got trained certified.